O[unreadable] Our interest is to elucidate the molecular basis of the difference in newborn and adult innate immunity, and study how two Tat proteins differentially affect dendritic cell (DC) functions. Purified adult and newborn DCs, pre-exposed to exogenous recombinant Tat proteins, are stimulated by toll like receptor and interferon signaling, and the expression of anti-viral or proinflammatory cytokines and activation of signaling/transcriptional pathways are investigated. It is postulated that anti-viral cytokine production may be impaired/underdeveloped in newborns, while they are efficient in proinflammatory cytokine induction. Tat proteins may alter the expression of transcription factors such as IRF7 and IRF8 to undermine effective host resistance.